Stepped pressure equilibrium with relaxed flow and applications in reversed-field pinch plasmas

Abstract

The Multi-region Relaxed MHD (MRxMHD) has been successful in the construction of equilibria in three-dimensional (3D) configurations. In MRxMHD, the plasma is sliced into sub-volumes separated by ideal interfaces, each undergoing relaxation, allowing the formation of islands and chaos. The resulting equilibrium has a stepped pressure profile across sub-volumes. The Stepped Pressure Equilibrium Code (SPEC) [S.R. Hudson et al., Phys. Plasmas 19, 112502 (2012)] was developed to calculate MRxMHD equilibria numerically. In this work, we have extended the SPEC code to compute MRxMHD equilibria with field-aligned flow and rotation, following the theoretical development to incorporate cross-helicity and angular momentum constraints. The code has been verified for convergence and compared to a Grad-Shafranov solver in 2D. We apply our new tool to study the flow profile change before and after the sawtooth crash of a reversed-field pinch discharge, in which data of the parallel flow is available. We find the promising result that under the constraints of cross-helicity and angular momentum, the parallel flow profile in post-crash SPEC equilibrium is flat in the plasma core and the amplitude of the flow matches experimental observations. Finally, we provide an example equilibrium with a 3D helical field structure as the favoured lower energy state. This will be the first 3D numerical equilibrium in which the flow effects are self-consistently calculated.

References in corpus (10)

• Computation of multi-region relaxed magnetohydrodynamic equilibria
• Rapid directional alignment of velocity and magnetic field in magnetohydrodynamic turbulence
• Nonaxisymmetric, multi-region relaxed magnetohydrodynamic equilibrium solutions
• The Infinite Interface Limit of Multiple-Region Relaxed MHD
• Variational formulation of relaxed and multi-region relaxed magnetohydrodynamics
• A minimally constrained model of self-organized helical states in reversed-field pinches
• Multi-region relaxed magnetohydrodynamics with flow
• Minimum energy states of the plasma pinch in standard and Hall magnetohydrodynamics
• Spectrum of multi-region-relaxed magnetohydrodynamic modes in topologically toroidal geometry
• Multi-region relaxed Hall magnetohydrodynamics with flow

Cited by in corpus (10)

• Time-dependent relaxed magnetohydrodynamics -- inclusion of cross helicity constraint using phase-space action
• On the non-existence of stepped-pressure equilibria far from symmetry
• Relaxed Magnetohydrodynamics with Ideal Ohm's Law Constraint
• Generalized Grad-Shafranov equation for non-axisymmetric MHD equilibria
• Nonlinear saturation of resistive tearing modes in a cylindrical tokamak with and without solving the dynamics
• Effects of Magnetic Helicity on 3D Equilibria and Self-Organized States in KTX Reversed Field Pinch
• Quasisymmetric magnetic fields in asymmetric toroidal domains
• Sawtooth crash in tokamak as a sequence of Multi-region Relaxed MHD equilibria
• The effect of shaping on turbulent dynamics in RFP simulations
• Near-ideal relaxed MHD in slab geometry